how to fix the P0301 code in my BMW 3 Series E90/E91 (2005-2012)?

Solution

1. Preparation

• Gather tools and parts needed for the repair.
• Disconnect the negative battery terminal to prevent electrical shorts.

Tools Required:

• OBD-II scanner
• Socket set
• Torque wrench
• Multimeter
• Compression tester

2. Inspect and Replace Ignition Components

• Ignition Coil Replacement:

  1. Remove the engine cover if necessary to access the ignition coil.
  2. Disconnect the electrical connector from the ignition coil.
  3. Remove the bolt securing the ignition coil and lift it out.
  4. Install the new ignition coil and secure it with the bolt.
  5. Reconnect the electrical connector.

• Spark Plug Replacement:

  1. Using a spark plug socket, remove the spark plug from cylinder 1.
  2. Inspect the old spark plug for signs of wear or damage.
  3. Gap the new spark plug to the manufacturer’s specifications (usually around 0.032-0.036 inches).
  4. Install the new spark plug and torque it to the specified value (typically 18-22 lb-ft).

3. Inspect and Clean Fuel Injector

1. Disconnect the fuel injector connector for cylinder 1.
2. Remove the fuel rail bolts and carefully lift the fuel rail with the injector attached.
3. Remove the injector from the rail and inspect it for dirt or clogs.
4. Clean the injector using a specialized injector cleaning solution or replace it if necessary.
5. Reinstall the fuel injector and secure the fuel rail back in place.

4. Check Engine Compression

1. Connect the compression tester to the spark plug hole for cylinder 1.
2. Crank the engine several times to get an accurate reading.
3. Compare the reading with manufacturer specifications (typically around 140-200 psi).
4. If compression is low, investigate further for potential internal engine issues.